This invention relates to the continuous treatment of particulate solids. In one of its aspects this invention relates to an apparatus for treating particulate solids in a series of fluidized beds. In another of its aspects this invention relates to a method for activating a continuous flow of particulate catalyst.
In the preparation of polymerization catalysts as described, for example, in U.S. Pat. Nos. 2,825,721 and 3,887,494, generally, such catalysts are activated in a batch operation with an oxygen-containing dry fluid, such as air, at temperatures ranging from about 350.degree. F (177.degree. C) to about 2000.degree. F (1093.degree. C) in a fluidized bed for about 0.1 hour to about 50 hours. In a commercial operation it would be particularly advantageous to be able to continuously activate such a catalyst so that freshly activated catalyst could be available for a polymerization process at any time. In seeking to develop such a continuous process we have discovered an apparatus and method in which not only particulate catalyst, especially ethylene polymerization catalyst comprising a chromium compound and silica or a silica admixed with up to about 20 weight percent of one or more metal oxides can be continuously activated to produce polymers of melt index comparable to the melt index produced using catalysts that have been activated batchwise, but also our treatment system is well adapted to the continuous treatment of particulate solids in other applications in which it is desirable to contact particulate material with hot gases in a fluidized bed.
It is therefore an object of this invention to provide method and apparatus for the multiple zone contacting of particulate solids with a treating gas. It is another object of this invention to provide method and apparatus for the activation of particulate catalysts, especially ethylene polymerization catalysts. It is still another object of this invention to provide activated particulate catalysts produced in a continuous activation process.
Other aspects, objects, and the various advantages of this invention will become apparent upon reading the specification and the appended claims in light of the drawings attached hereto.